The speaker of Brazil's lower house vowed Wednesday to fight any changes President Michel Temer makes to a labor reform bill passed by the Senate, highlighting new tension between longtime political allies.

The speaker, Rodrigo Maia, would replace Temer if Congress allows the Supreme Court to move ahead with a corruption charge against the president, a vote that Maia has said he wants to have this week.

The bill, a business-friendly measure modernizing labor laws dating from the 1940s, passed by a wide margin in the Senate on Tuesday following approval in the lower house and will be sent to Temer to be signed into law.

Given that any changes in the Senate would have sent the bill back to the lower house for fresh debate, Temer assured senators Tuesday that he would use a decree to tweak the legislation as they suggested after he signed it into law.

Maia rejected any such arrangement.

"The lower house will not accept any change to the law. Any [presidential decree] will not be recognized by the House," the speaker said in a Twitter post.

Graft scheme

Prosecutors charged Temer last month in a graft scheme involving JBS SA, the world's biggest meatpacker. Executives said the president took bribes from the company in exchange for resolving tax matters and facilitating loans from state-run banks.

Temer has repeatedly denied any wrongdoing.

The presidential press office said in a statement that Maia has remained loyal to Temer since becoming speaker last year.

"The presidential palace rebuffs the attempts to create a false crisis between the executive and legislative power without connection to facts and reality," the statement said.

Under Brazilian law, two-thirds of the lower house of Congress must vote to allow a criminal charge against a sitting president to move to the Supreme Court. The vote could happen Friday or possibly be delayed until early August, after a congressional recess.